PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Robert Clergerie Slip On Leather Loafers Platform Shoes Size 8.5BCBG Paris Shoes 9.5 / 40.5 Womens Brown Leather Square Toe Loafers 1.5" Heel , AIR STEP GRAY SHOES WOMENS SIZE 10 ELLEN , Women's Light Weight Flat Running Sport Athlet Sneaker Shoes Size 5 - 10 NEWWomen's Vintage TOMMY HILFIGER Flagged Black Leather Mule Clogs-Size 6M , Women’s Multi Brown Leather Merrell Eden Moc Slingback Shoes Size 6.5 , CLARKS Collection Bendables Womens Black Loafers Crocodile Print Design 7.5MKlogs Reese Women's Slip On Leather Shoes Display Model Black/Lunar 9.5 M , Demonia 5.25" Wedge Heel Vegan Suede Purple & Leopard Creepers Goth Mod 6-11Chic Womens Leather Formal Low Block Heels Loafers Slip On Moccasins Shoes New , MERRELL US 7.5 Bracken Brown Leather Slip On Mocs Warm Sport Shoes Oxfords 38 , (H-8) Brooks Asteria Women SIZE 6.5 Medium (B) Running Shoes , Keds Women's Champion Navy Slip-On Shoes - Size 6Nike Flex Air Max Womens Size 6 Running Shoes Pink And BluePuma iocell 1.0 Cell Riaze Foil Training Shoe, Womens Sz 6.5. , Merrell Nylon Casual Walking Trail Mary Jane Shoes Women's Size 11 , KENDALL + KYLIE Women's Rae Sneaker, Navy, Size 9.5 gibLBARELY USED!!! DREW Womans WHITE LEATHER Shoes Size 6.5 , New Womens Nike Son Of Force Athletic Shoes Sneakers 616302-006 sz 8 Black , Bearpaw Women's Willow Boots Charcoal 5Nike Size 9 Black Court Shoes Women'sSkechers S Sports 11635 Women's Gray Purple Athletic Sneaker Gym Shoes Sz 6.5 , Saucony Ride 10 White/Purple/Blue Running Shoes Women's US 8 (O2,21)Etnies Womens Scout XT Sneaker Tan Size 6 Brand New With Box?$80 , Adidas Women's Originals Tubular Viral2 W Utility Black/White BY9745 - BRAND NEW , CONVERSE Chuck Taylor All Star Low Top Shoes Unisex Canvas Sneakers *NEW*NEW NIKE Women's Size 8.5 Free TR 6 Training Run Shoes Black/Crimson 833424-006Propet Wash & Wear Slip-Ons-Women's size 6.5 M MerlotAsics Gel-Enhance Ultra 3.0 Athletic Shoes - Women's Size 8.5, NavyExcellent ASICS GEL-CUMULUS 18 2016 Womens 10, 42 EUR Blue Red $120 ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."